JP6917027B2 - Polyimide fiber and its manufacturing method - Google Patents

Description

The present invention relates to a polyimide fiber and a method for producing the same, and more particularly to a high-performance polyimide fiber produced from a solvent-soluble polyimide and a method for producing the same.

Nylon and polyester fibers are mainly used as fibers used for clothing, tire cords and fishing nets. Fibers that exhibit more than twice the strength, high melting point, and high decomposition temperature are said to be high-performance fibers. Polyimide fibers are also known as high performance fibers.

Patent Document 1 discloses a polyimide fiber composed of pyromellitic acid dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (DADE). Since this polyimide is sparingly soluble in a solvent such as N-methylpyrrolidone (NMP), a polyamic acid solution, which is a precursor, is used as a spinning solution to produce polyimide fibers, and the polyamic acid fibers are prepared by a dry spinning method. An imidization step of manufacturing and further performing heat treatment at a high temperature of 350 ° C. or higher is required.

Patent Document 2 describes the reaction between a tetracarboxylic acid component containing 2,3,3', 4'-biphenyltetracarboxylic dianhydride (a-BPDA) and a diamine component containing toluene diisocyanate or toluenediamine. The filaments of the polyimide used are described. As a production method, a method of producing fibers by a wet spinning method (particularly, a semi-dry wet spinning method) or a dry spinning method using a polyimide solution obtained by reacting these components in an aprotic polar solvent as a spinning solution is available. Has been described. However, when water or ethanol is used as the coagulation bath of the wet spinning method (semi-dry wet spinning method), there is a problem that the fibers are whitened (white turbid). Further, even in the case of the dry spinning method, since the washing step with water is included to remove the solvent in the obtained fiber, the advantage of using an expensive dry spinning device is not utilized, and it is an industrially advantageous method. do not have.

Patent Document 3 describes tetracarboxylic dianhydrides, specifically 3,3', 4,4'-biphenyltetracarboxylic dianhydrides (s-) on the amino groups at both ends of bis (aminophenoxy) biphenyl. Described are fibers obtained from a polyimide having a structure to which BPDA) is added. Since this polyimide can be used as a solvent, the polyimide fiber can be produced by a wet spinning method using a polyimide solution as a spinning solution and a mixed solvent of water, water and alcohol as a coagulation bath. However, the polymerization step for obtaining a spinning solution is complicated including a first polymerization step of preparing an oligomer and a second polymerization step of reacting the oligomer with tetracarboxylic acid dianhydride and diamine to prepare an imide polymer. Because it is a simple process, it is disadvantageous as an industrial manufacturing method.

Japanese Unexamined Patent Publication No. 2009-228189 Japanese Unexamined Patent Publication No. 2010-180494 Japanese Unexamined Patent Publication No. 2013-117015

There is a need for a polyimide fiber having excellent heat resistance and mechanical properties and industrially advantageous to be produced, and a method for producing the same. The present invention has been made to solve these problems, and an object of the present invention is to provide a novel polyimide fiber having excellent heat resistance and mechanical properties, and an industrially advantageous manufacturing method thereof.

（式中、Ｘ_１は、テトラカルボン酸成分に由来する４価の基であり、Ｙ_１は、ジアミン成分に由来する２価の基であり、
前記テトラカルボン酸成分は、２，３，３’，４’−ビフェニルテトラカルボン酸二無水物を５０〜８５モル％含み、前記ジアミン成分は、フェノール性水酸基を含有するジアミン化合物を１０モル％以上含む。）
で表される構造を有することを特徴とする、ポリイミド繊維。 The present invention relates to the following matters.
1. 1. A polyimide fiber containing a polyimide having a structure obtained by a reaction between a tetracarboxylic acid component and a diamine component.
The polyimide has the following formula (1):

(In the formula, X ₁ is a tetravalent group derived from the tetracarboxylic acid component, and Y ₁ is a divalent group derived from the diamine component.
The tetracarboxylic acid component contains 50 to 85 mol% of 2,3,3', 4'-biphenyltetracarboxylic dianhydride, and the diamine component contains 10 mol% or more of a diamine compound containing a phenolic hydroxyl group. include. )
A polyimide fiber having a structure represented by.

2. A compound in which the tetracarboxylic acid component is further selected from the group consisting of 3,3', 4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and 4,4'-oxydiphthalic acid anhydride. The polyimide fiber according to Item 1 above, which comprises.

3. 3. The diamine compounds containing a phenolic hydroxyl group are bis (3-amino-4-hydroxyphenyl) sulfone, 4,4'-diamino-3,3'-dihydroxy-1,1'-biphenyl and 2,2'-. Item 2. The polyimide fiber according to Item 1 or 2, which comprises at least one selected from the group consisting of bis (3-amino-4-hydroxyphenyl) hexafluoropropane.

4. Any of the above items 1 to 3, wherein the glass transition temperature is 310 ° C. or higher, the elongation is 5% or higher, the tensile elastic modulus is 2 GPa or higher, the tensile strength is 100 MPa or higher, and the thickness is 0.1 to 50 denier. The polyimide fiber according to item 1.

5. A step of preparing a polyimide solution in which the polyimide defined in any one of the above items 1 to 3 is dissolved, and the polyimide solution is discharged from a nozzle in a gas, and then contains 50 wt% or more of water. A method for producing a polyimide fiber, which comprises a step of immersing in a coagulation bath.

6. Item 5. The method for producing a polyimide fiber according to Item 5, further comprising a step of stretching the coagulated fiber taken from the coagulating liquid in a temperature range of 200 to 400 ° C.

According to the present invention, it is possible to provide a novel polyimide fiber which is excellent in heat resistance and mechanical properties and can be produced industrially advantageously, and an industrially advantageous production method thereof.

It is a figure which shows typically the spinning apparatus. It is a figure which shows typically the structure of the heat stretching apparatus.

The polyimide fiber of the present invention is obtained by spinning a polyimide-containing solution (spinning dope) obtained by reacting a tetracarboxylic acid component with a diamine component.

The tetracarboxylic acid component includes tetracarboxylic acid, tetracarboxylic dianhydride, and other tetracarboxylic acid derivatives such as tetracarboxylic acid silyl ester, tetracarboxylic acid ester, and tetracarboxylic acid chloride, which are used as raw materials for producing polyimide. .. Although not particularly limited, it is convenient to use tetracarboxylic dianhydride in production, and the following description describes an example in which tetracarboxylic dianhydride is used as the tetracarboxylic dianhydride component. The diamine component is a diamine compound used as a raw material for producing polyimide.

で表される構造単位を含有し、式中、Ｘ_１は、テトラカルボン酸成分に由来する４価の基、即ちテトラカルボン酸から４個のカルボン酸基を除いた残基であり、Ｙ_１は、ジアミン成分に由来する２価の基、即ちジアミンから２つのアミン基を除いた残基である。 Hereinafter, the polyimide, the spinning dope, and the spinning method constituting the polyimide fiber of the present invention will be described.
[Polyimide]
The polyimide used for producing the polyimide fiber has the following formula (1):

In the formula, X ₁ is a tetravalent group derived from the tetracarboxylic acid component, that is, a residue obtained by removing 4 carboxylic acid groups from the tetracarboxylic acid, and Y ₁ Is a divalent group derived from the diamine component, that is, a residue obtained by removing two amine groups from diamine.

Polyimide is obtained by reacting a tetracarboxylic acid component and a diamine component, and in the above formula (1), X ₁ and Y ₁ are introduced based on the tetracarboxylic acid component and the diamine component, respectively. The structure of polyimide will be described by explaining the tetracarboxylic acid component and the diamine component used in the production.

The tetracarboxylic acid component contains 2,3,3', 4'-biphenyltetracarboxylic dianhydride (a-BPDA) in a proportion of preferably 50 mol% or more, more preferably 60 mol% or more. If the amount of a-BPDA is too small, it may not be possible to prepare a dope suitable for spinning because the reaction solution becomes a gel or insoluble matter precipitates. The upper limit of the proportion of a-BPDA is preferably 90 mol% or less, more preferably 85 mol% or less, and more preferably 80 mol% or less in a specific embodiment. If the amount of a-BPDA is too large, the viscosity of the reaction solution may not increase.

As the tetracarboxylic acid component, the other tetracarboxylic dianhydride used in combination with a-BPDA is preferably an aromatic tetracarboxylic dianhydride from the viewpoint of mechanical properties and heat resistance. Specifically, for example, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic anhydride, 3 , 3', 4,4'-benzophenonetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, and 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane Dianhydride and the like can be mentioned. As the combined tetracarboxylic dianhydride, one kind may be used, or two or more kinds may be used. Among these, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic dianhydride (PMDA) and 4,4'-oxydiphthalic anhydride are preferable. In particular, the inclusion of 3,3', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and / or pyromellitic dianhydride (PMDA) improves the mechanical properties of the resulting fiber. It is preferable because it does.

The diamine component contains a diamine compound containing a phenolic hydroxyl group in a proportion of preferably 10 mol% or more, more preferably 13 mol% or more, and more preferably 20 mol% or more in a specific embodiment. By containing the diamine compound containing a phenolic hydroxyl group, whitening of the fiber generated when the spinning dope is immersed in the coagulating liquid in the spinning process is suppressed, and a high-performance fiber can be obtained. If the diamine compound containing a phenolic hydroxyl group is contained in the above ratio, whitening of the fiber can be suppressed, so that it is not necessary to contain the diamine compound in an unnecessarily large amount and it can be appropriately set. The content ratio can be set to, for example, 80 mol% or less, more preferably 70 mol% or less.

The diamine compound containing a phenolic hydroxyl group may have a benzene ring in which at least one OH group is bonded in the molecule, thereby exhibiting an appropriate affinity with water and whitening the fiber during spinning. Can be suppressed. For example, a compound having 1 to 3 hydroxyphenyl rings and having a direct bond or a linking group between the phenyl rings can be mentioned. More specifically, for example, equations (2-1) and (2-2):

（式中、Ｗ_１は直接結合または２価の有機基である。）
で表される化合物が挙げられる。２価の有機基としては、例えば、−ＣＨ_２−、−Ｏ−、−ＣＯ−、−ＳＯ_２−、−Ｓ−、−Ｃ（ＣＨ_３）_２−、および−Ｃ（ＣＦ_３）_２−等を挙げることができる。

(In the formula, W ₁ is a direct bond or a divalent organic group.)
Examples thereof include compounds represented by. Divalent organic groups include, for example, -CH _2- , -O-, -CO-, -SO _2- , -S-, -C (CH ₃ ) _2- , and -C (CF ₃ ) _2- And so on.

Specific compounds include, for example, bis (3-amino-4-hydroxyphenyl) sulfone (HOAB), 4,4'-diamino-3,3'-dihydroxy-1,1'-biphenyl (HAB) and 2 , 2'-Bis (3-amino-4-hydroxyphenyl) hexafluoropropane and the like.

As the diamine component, the other diamine compound used in combination with the diamine compound containing a phenolic hydroxyl group is preferably an aromatic diamine compound from the viewpoint of mechanical properties and heat resistance. Specifically, for example, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 4,4-diamino-3,3'-dimethyl-1,1'-biphenyl, 4,4'diamino- 3,3'-Dimethoxy-1,1'-biphenyl, 4,4'-diaminodifemilmethane, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether (DADE), 3,3'-diamino Diphenyl sulphon, 4,4'-diaminodiphenyl sulphon, 4,4'-diaminodiphenyl sulfide, 2,2'-bis (4-aminophenyl) propane, 2,2'-bis (4-aminophenyl) hexafluoropropane , 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl (BABP), 2,2'-bis [4- (4-Aminophenoxy) phenyl] propane, 2,2'-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, bis [4- (3-aminophenoxy) phenyl] sulfone (mBAPPS) , Bis [4- (4-aminophenoxy) phenyl] sulphon (BAPPS), 3,5-diaminobenzoic acid, 2,5-diaminopyridine, 2,6-diaminopyridine, 2,6-diamino-4-methylpyridine , 4,4'-(9-fluorenylidene) dianiline, diaminocyclohexane compound (1,4-diaminocyclohexane, etc.) and the like. These may be used alone or in combination of two or more.

Among the above, as other diamine compounds to be used in combination, DADE and BABP are preferable from the viewpoint of being able to increase the viscosity and concentration of the reaction solution and improving the elongation at break.

[Spinning dope]
When producing the polyimide fiber of the present invention, it is preferable to use the solution prepared with the polyimide as it is as a spinning dope (spinning liquid). It is also possible to obtain a polyimide as a solid and then dissolve it in a solvent to produce a polyimide solution and use it as a spinning dope, but usually, as described below, a tetracarboxylic acid component and a diamine component are contained in the solvent. It is preferable to dilute or concentrate the polyimide solution obtained by the reaction in (1) as it is, if necessary, and use it as a spinning dope.

The polyimide solution can be prepared by reacting a tetracarboxylic acid component (for example, tetracarboxylic dianhydride) and a diamine component (diamine compound) in a solvent until polymerization and imidization proceed (complete). The polymerization / imidization reaction can be carried out in the same manner as before. For example, a method of synthesizing a polyimide precursor from tetracarboxylic dianhydride and diamine and imidizing it in the presence of an imidization catalyst; similarly, imide by synthesizing a polyimide precursor and directly heating it. Method of forming; Examples thereof include known reaction / production methods such as a method of polycondensing tetracarboxylic acid dianhydride and diamine in a solvent at a high temperature. Further, a chemical imidization method can also be adopted by synthesizing a polyimide precursor and adding a dehydrating agent and, if necessary, a cyclization catalyst to the polyimide precursor.

Further, as described in Patent Document 3 (Japanese Patent Laid-Open No. 2013-117015), an oligomer is first prepared by a combination of specific components (first-stage polymerization), and the tetracarboxylic acid component and the tetracarboxylic acid component are further added to the oligomer. It can also be produced by a method of reacting a diamine component (second-stage polymerization) (two-stage polymerization method; two-stage addition method). However, if the composition of the combination of the tetracarboxylic acid component and the diamine component specified in the present invention is used, it is not necessary to use the two-step polymerization method as in Patent Document 3, and the solvent-soluble polyimide can be produced by the one-step polymerization reaction. can. For example, the diamine component may be added to the solvent to dissolve it, and then the tetracarboxylic acid component may be added to proceed the reaction. Alternatively, the polyimide precursor (polyamic acid) may be produced once (reaction at a relatively low temperature such as room temperature) and then imidization may proceed, but the tetracarboxylic acid component and the diamine component may be mixed in a solvent. A method of polycondensation at a high temperature is convenient and preferable, and a solvent-soluble polyimide can be produced by this method using the composition of the present invention.

When performing high-temperature polycondensation in one step, an imidization catalyst and / or a product water removing agent (for example, an azeotropic solvent such as toluene) may be added if necessary. The reaction temperature is, for example, 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 130 ° C. or higher, and for example, the boiling point or lower of the solvent used or 300 ° C. or lower, more preferably 250 ° C. or lower. The polymerization reaction is preferably carried out in an atmosphere of an inert gas such as nitrogen.

The polycondensation solvent is preferably an aproton polar organic solvent, and examples thereof include γ-butyrolactone, N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide, and 1,3-dimethylimidazolidone. These can be used alone or in combination.

The polyimide solution produced as described above can be used as it is as a spinning dope, or if necessary, diluted or concentrated to be used as a spinning dope.

The viscosity of the spun dope (or the polyimide solution after polymerization) used in the production of the polyimide fiber is preferably 20 to 3000 poise at 30 ° C. Further, 50 to 500 poise is preferable in order to continuously obtain fibers having spinnability and without thread breakage. A dope having a viscosity of several thousand poises can be continuously spun without yarn breakage by reducing the viscosity to 50 to 500 poises by heating the dope. The polyimide solid content concentration in the spinning dope (or the polyimide solution after polymerization) is not limited, but is usually 10 to 40% by mass, preferably 10 to 30% by mass.

The spinning dope may contain an additive, if necessary, and examples thereof include lubricants and fillers.

[Polyimide fiber and its manufacturing method]
The polyimide fiber of the present invention can be produced by a wet spinning method (including a semi-dry wet spinning method) or a dry spinning method. However, by using the composition of the present invention, the fibers are not whitened even if the wet spinning method using a water-based coagulation bath, which is advantageous in terms of cost, is adopted, so that a polyimide fiber having excellent mechanical properties can be produced. .. Therefore, in the present invention, the wet spinning method is preferable, and the semi-dry wet spinning method is particularly preferable.

An example of the semi-dry wet spinning method will be described with reference to the drawings. FIG. 1 is a diagram schematically showing an example of a semi-dry wet spinning method. The spinning dope 10 is extruded from the nozzle 11 and discharged into a gas layer (for example, in the air) in the form of filaments (filament liquid 1), and then the filament liquid 1 is guided to the coagulation bath 20 by rollers (12, 13, 14). While being conveyed, it is coagulated in the coagulating liquid 20 and pulled up from the coagulation bath as a coagulating thread 2 and wound on a winding device 15 (for example, a bobbin).

The distance of the gas layer from which the filament liquid 1 is discharged (from the tip of the nozzle until the filament touches the coagulation bath) is not limited, but if it is too short, the poor solvent comes into contact with the nozzle due to the wave motion of the liquid surface, and sufficient flow stretching is performed. It may not be possible, and if it is too long, the monofilaments may sway and come into contact with each other to combine threads. Generally, the distance between the gas layers is preferably 5 to 30 mm.

The coagulation liquid used in the coagulation bath is not particularly limited, but in the present invention, it is possible to use an water-based coagulation liquid that does not impose an environmental load, and specifically, water and a mixture with water. Examples thereof include a mixture of possible organic solvents, such as a mixed solvent of water and an alcohol (preferably an alcohol having 3 or less carbon atoms such as ethanol and propanol). The residence time of the discharged filament in the coagulation bath needs to be at least enough to coagulate the coagulated yarn.

The coagulating yarn 2 pulled up from the coagulation bath is wound on a winding device 15 (for example, a bobbin). Since the coagulated yarn contains a large amount of solvent, for example, it is heated in the order of 50 → 100 ° C. → 200 ° C. to evaporate and remove the residual solvent. This drying can be performed before and after winding on the winding device, but it is also preferable to dry the product while it is wound on the bobbin. For the spinning nozzle diameter and spinning draft ratio (V1 / V0; where V1 is the winding speed by the winding device 15 and V0 is the discharge speed from the nozzle 11), the target fiber diameter and the stability of the manufacturing process are taken into consideration. Can be decided. As an example, the spinning nozzle diameter can be appropriately set in the range of about 10 μm to 1 mm, and the spinning draft ratio can be appropriately set in the range of about 2 to 100.

Since the present invention can produce fibers from the polyimide solution by the wet spinning method, there is an advantage that the production process of the polyimide fibers can be simplified.

The fiber from which the solvent has been removed can be used as it is depending on the application, but the mechanical properties such as the tensile strength and elastic modulus of the fiber can be improved by further heat drawing. When a polyimide fiber (including coagulated yarn) containing a solvent such as NMP is passed through a heating furnace, it melts and the yarn breaks, and continuous heat treatment cannot be performed. Therefore, it is preferable to heat-stretch the fiber in which the solvent is reduced by drying. .. The amount of residual solvent in the polyimide fiber to be heat-stretched is preferably 10% by mass or less, more preferably 5% by mass or less.

In the heat-stretching treatment, for example, as shown in FIG. 2, the polyimide fiber 3 which has been subjected to the drying treatment of the solvent is unwound from the roll 31 (for example, bobbin), and while being passed through the heating furnace 30, the polyimide is stretched and stretched. Obtain fiber 4. The draw ratio can be determined by the ratio V3 / V2 of the winding speed V3 of the winding device 32 and the feeding speed V2 of the roll 31. The heating temperature is, for example, 200 to 400 ° C., and the stretching ratio is from more than 1 to, for example, about 20.

The polyimide fiber of the present invention is excellent in heat resistance and mechanical properties in addition to being able to be manufactured by a simple manufacturing method. The polyimide fiber of the present invention has a glass transition temperature of 310 ° C. or higher, preferably 320 ° C. or higher, usually 380 ° C. or lower, and a breaking elongation of 5% or higher, preferably 10% or higher, usually 100. % Or less, tensile elastic modulus is 2 GPa or more, preferably 4 GPa or more, usually 150 GPa or less, tensile strength is 100 MPa or more, preferably 200 MPa or more, usually 1000 MPa or less, and thickness is 0. .1 to 50 denier.

If necessary, the surface of the obtained polyimide fiber can be coated with a surfactant, an oil agent, or other chemicals. Further, the cross section of the polyimide fiber of the present invention is not limited to a circular shape, and may have various shapes. The polyimide fiber of the present invention can be used in various applications where strength and heat resistance are required. For example, since the fiber diameter is small and the strength is strong, it is also suitable for screen printing plate fibers and the like.

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples.

[Measuring method]
For the thermal analysis sample, a polyimide solution was cast on a glass plate, dried at a temperature of 150 ° C. for 30 minutes, the produced film was peeled off from the glass plate, fixed to a metal frame, and dried at 300 ° C. for 30 minutes. board.
For thermogravimetric analysis (TGA) and differential thermal analysis (DTA), DTG-60 manufactured by Shimadzu Corporation was used as a simultaneous measuring device. For differential scanning calorimetry (DSC), a DSC-60 manufactured by Shimadzu Corporation was used as a measuring device.
The glass transition temperature was determined by dynamic thermomechanical measurement (DMA) using a measuring device manufactured by SII Nanotechnology.

Molecular Weight For the measurement of the molecular weight, HLC-83206PC Eco SEC manufactured by Tosoh Co., Ltd. was used as a measuring device. The molecular weight was calculated with reference to standard polystyrene.

Mechanical properties (modulus, elongation, strength)
The tensile test was carried out using a universal material testing machine 33442 measuring device manufactured by Instron in accordance with JIS L 1095 at a distance between chucks of 20 mm, and elastic modulus, breaking elongation and breaking strength were measured.

Measurement of Polyimide Solution Viscosity The viscosity of the polyimide solution was measured at 30 ° C. using BLOOK FIELD DV-E VISCOMETER.

Use the following abbreviations.
HOAB: Bis (3-amino-4-hydroxyphenyl) Sulfon HAB: 4,4'-diamino-3,3'-dihydroxy-1,1'-biphenyl BABP: 4,4'-bis (4-aminophenoxy) Biphenyl DADE: 4,4'-diaminodiphenyl ether BAPPS: bis [4- (4-aminophenoxy) phenyl] sulphon mBAPPS: bis [4- (3-aminophenoxy) phenyl] sulphon a-BPDA: 2,3,3' , 4'-biphenyltetracarboxylic acid dianhydride s-BPDA: 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride PMDA: pyromellitic acid dianhydride

[Preparation of polyimide]
(Example 1)
190 g of solvent NMP, 6.33 g of HOAB, and 12.72 g of BABP were added to a three-necked flask having a volume of 0.5 L and stirred. After confirming the dissolution, 15.03 g of a-BPDA and 5.01 g of s-BPDA were added, and the resulting water was removed from the system by azeotrope with toluene, and the mixture was stirred at 180 ° C. for 4 hours to make a viscous polyimide. Spinning dope was prepared. The viscosity of the obtained polymerization solution was 600 poise, and the weight average molecular weight was 139,000.

(Examples 2 to 13)
A polyimide spinning dope was prepared in the same manner as in Example 1 except that the tetracarboxylic acid component and the diamine component shown in Table 1 were used. The results are shown in Tables 1a to 1e.

(Comparative Examples 1 to 3)
A polyimide spinning dope was prepared in the same manner as in Example 1 except that the tetracarboxylic acid component and the diamine component shown in Table 2 were used. The results are shown in Table 2. In Comparative Examples 1 and 2 in which only a-BPDA was used as the tetracarboxylic acid component, the viscosity of the polymer solution did not increase, and a viscous dope suitable for spinning could not be obtained.

(Comparative Example 4)
Polymerization by the method (polymerization method A) of Patent Document 3 (Japanese Patent Laid-Open No. 2013-117015) s-BPDA (5.84 g), HOAB (5.60 g), DADE (4.0 g), Valerolactone (2.0 g), Pyridine (3.0 g) was added, and NMP (180 g) and toluene (20 g) were added. The mixture was stirred at room temperature with nitrogen passing through, and after 10 minutes, the reactor was heated to 180 ° C. using an oil bath and reacted at 180 rpm (stirring) for 40 minutes (first stage polymerization). Then, it was air-cooled, s-BPDA (11.76 g), BABP (7.36 g) and NMP (190 g) were added, and the reaction was carried out at 180 ° C. (second stage polymerization). After the reaction for 3 hours, the reactor was pulled out of the oil bath to stop the reaction. A 600 poise polyimide solution was obtained.

(Comparative Examples 5 and 6)
A polyimide spinning dope was prepared in the same manner as in Example 1 except that the tetracarboxylic acid component and the diamine component shown in Table 3 were used.

As shown in Table 3, in Comparative Example 4 in which the two-stage polymerization was adopted, the polyimide spinning dope could be produced, but the process was complicated. In Comparative Example 5, the same composition as in Comparative Example 4 was used, and the same one-step polymerization as in Example 1 was used for polymerization, but a yellow precipitate was formed and a dope suitable for spinning could not be obtained. The composition of Comparative Example 6 contained a-BPDA, but due to the small amount, the polymerization solution became a gel, and a dope suitable for spinning could not be obtained.

[Manufacturing of polyimide fiber]
Polyimide fibers were produced using the polyimide spinning dope of Examples 1 to 13 and Comparative Example 3 shown in Table 1. As the manufacturing apparatus, the spinning apparatus shown in FIG. 1 and the heating and stretching apparatus shown in FIG. 2 were used. Using a hole diameter of 300 μm × 5 holes as a nozzle, the spinning dope was discharged into a coagulation bath of water (room temperature). Adjust the back pressure so that the discharge speed (V0) is 1 to 20 m / min and the winding speed (V1) is 10 to 100 (Max) m / min. Hastened. The draft ratio (V1 / V0) was set to 5 to 20.

The spun coagulated yarn was dried or air-dried at a temperature of 50 ° C., then rewound on an aluminum bobbin and heated at 200 ° C. for 30 minutes, and the fiber from which NMP in the fiber was removed was used as a heat treatment fiber. The residual NMP of the dried fibers of Example 1 was 2.3%. The heating furnace (electric furnace) length of the heating stretching apparatus was 90 cm, and the temperature was maintained at 200 to 400 ° C. As shown in FIG. 2, the delivery speed V2 was set to 2.21 m / min, and the take-up speed V3 was set to 4.42 m / min to 22.1 m / min. The draw ratio (V3 / V2) is 2 to 10.

The dope of Comparative Example 3 could be continuously and stably spun, but the surface of the obtained fiber was whitened and the tensile strength was low, so that a high-performance fiber could not be obtained. Table 4 shows the characteristics of the spun, dried, and heat-stretched fibers.

As shown in Table 4, polyimide fibers having a glass transition temperature of 310 ° C. or higher, a breaking elongation of 5% or higher, an elastic modulus of 2 GPa or higher, and a breaking strength of 100 MPa or higher are excellent in heat resistance and mechanical properties. , It was found that it can be obtained by a simple manufacturing method.

The polyimide fiber provided by the present invention has excellent heat resistance and mechanical properties, and can be used in fields requiring heat resistance, flame retardancy and high mechanical properties.

1 Filament liquid 2 Coagulated yarn 3 Solvent-dried polyimide fiber 4 Stretched polyimide fiber 10 Spinned dope 11 Nozzle 12, 13, 14 Roller 15 Winding device 20 Coagulation bath 30 Heating furnace 31 Roll 32 Winding device

Claims (6)

A polyimide fiber containing a polyimide having a structure obtained by a reaction between a tetracarboxylic acid component and a diamine component.
The polyimide has the following formula (1):

(In the formula, X ₁ is a tetravalent group derived from the tetracarboxylic acid component, and Y ₁ is a divalent group derived from the diamine component.
The tetracarboxylic acid component contains 50 to 85 mol% of 2,3,3', 4'-biphenyltetracarboxylic dianhydride, and the diamine component contains 10 mol% or more of a diamine compound containing a phenolic hydroxyl group. include. )
A polyimide fiber having a structure represented by. A compound in which the tetracarboxylic acid component is further selected from the group consisting of 3,3', 4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and 4,4'-oxydiphthalic acid anhydride. The polyimide fiber according to claim 1, which comprises. The diamine compounds containing a phenolic hydroxyl group are bis (3-amino-4-hydroxyphenyl) sulfone, 4,4'-diamino-3,3'-dihydroxy-1,1'-biphenyl and 2,2'-. The polyimide fiber according to claim 1 or 2, which comprises at least one selected from the group consisting of bis (3-amino-4-hydroxyphenyl) hexafluoropropane. Any of claims 1 to 3, wherein the glass transition temperature is 310 ° C. or higher, the elongation is 5% or higher, the tensile elastic modulus is 2 GPa or higher, the tensile strength is 100 MPa or higher, and the thickness is 0.1 to 50 denier. The polyimide fiber according to item 1. A step of preparing a polyimide solution in which the polyimide defined in any one of claims 1 to 3 is dissolved, and the polyimide solution is discharged from a nozzle in a gas, and then contains 50 wt% or more of water. A method for producing a polyimide fiber, which comprises a step of immersing in a coagulation bath. The method for producing a polyimide fiber according to claim 5, further comprising a step of stretching the coagulated fiber taken from the coagulating liquid in a temperature range of 200 to 400 ° C.

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